| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.rya.mongodb.aggregation; |
| |
| import java.util.Map; |
| |
| import org.bson.Document; |
| import org.eclipse.rdf4j.common.iteration.CloseableIteration; |
| import org.eclipse.rdf4j.model.Value; |
| import org.eclipse.rdf4j.model.ValueFactory; |
| import org.eclipse.rdf4j.model.impl.SimpleValueFactory; |
| import org.eclipse.rdf4j.model.vocabulary.XMLSchema; |
| import org.eclipse.rdf4j.query.Binding; |
| import org.eclipse.rdf4j.query.BindingSet; |
| import org.eclipse.rdf4j.query.QueryEvaluationException; |
| import org.eclipse.rdf4j.query.algebra.evaluation.QueryBindingSet; |
| |
| import com.google.common.base.Preconditions; |
| import com.mongodb.client.AggregateIterable; |
| import com.mongodb.client.MongoCursor; |
| |
| /** |
| * An iterator that converts the documents resulting from an |
| * {@link AggregationPipelineQueryNode} into {@link BindingSet}s. |
| */ |
| public class PipelineResultIteration implements CloseableIteration<BindingSet, QueryEvaluationException> { |
| private static final int BATCH_SIZE = 1000; |
| private static final ValueFactory VF = SimpleValueFactory.getInstance(); |
| |
| private final MongoCursor<Document> cursor; |
| private final Map<String, String> varToOriginalName; |
| private final BindingSet bindings; |
| private BindingSet nextSolution = null; |
| |
| /** |
| * Constructor. |
| * @param aggIter Iterator of documents in AggregationPipelineQueryNode's |
| * intermediate solution representation. |
| * @param varToOriginalName A mapping from field names in the pipeline |
| * result documents to equivalent variable names in the original query. |
| * Where an entry does not exist for a field, the field name and variable |
| * name are assumed to be the same. |
| * @param bindings A partial solution. May be empty. |
| */ |
| public PipelineResultIteration(AggregateIterable<Document> aggIter, |
| Map<String, String> varToOriginalName, |
| BindingSet bindings) { |
| this.varToOriginalName = Preconditions.checkNotNull(varToOriginalName); |
| this.bindings = Preconditions.checkNotNull(bindings); |
| Preconditions.checkNotNull(aggIter); |
| aggIter.batchSize(BATCH_SIZE); |
| this.cursor = aggIter.iterator(); |
| } |
| |
| private void lookahead() { |
| while (nextSolution == null && cursor.hasNext()) { |
| nextSolution = docToBindingSet(cursor.next()); |
| } |
| } |
| |
| @Override |
| public boolean hasNext() throws QueryEvaluationException { |
| lookahead(); |
| return nextSolution != null; |
| } |
| |
| @Override |
| public BindingSet next() throws QueryEvaluationException { |
| lookahead(); |
| BindingSet solution = nextSolution; |
| nextSolution = null; |
| return solution; |
| } |
| |
| /** |
| * @throws UnsupportedOperationException always. |
| */ |
| @Override |
| public void remove() throws QueryEvaluationException { |
| throw new UnsupportedOperationException("remove() undefined for query result iteration"); |
| } |
| |
| @Override |
| public void close() throws QueryEvaluationException { |
| cursor.close(); |
| } |
| |
| private QueryBindingSet docToBindingSet(Document result) { |
| QueryBindingSet bindingSet = new QueryBindingSet(bindings); |
| Document valueSet = result.get(AggregationPipelineQueryNode.VALUES, Document.class); |
| Document typeSet = result.get(AggregationPipelineQueryNode.TYPES, Document.class); |
| if (valueSet != null) { |
| for (Map.Entry<String, Object> entry : valueSet.entrySet()) { |
| String fieldName = entry.getKey(); |
| String valueString = entry.getValue().toString(); |
| String typeString = typeSet == null ? null : typeSet.getString(fieldName); |
| String varName = varToOriginalName.getOrDefault(fieldName, fieldName); |
| Value varValue; |
| if (typeString == null || typeString.equals(XMLSchema.ANYURI.stringValue())) { |
| varValue = VF.createIRI(valueString); |
| } |
| else { |
| varValue = VF.createLiteral(valueString, VF.createIRI(typeString)); |
| } |
| Binding existingBinding = bindingSet.getBinding(varName); |
| // If this variable is not already bound, add it. |
| if (existingBinding == null) { |
| bindingSet.addBinding(varName, varValue); |
| } |
| // If it's bound to something else, the solutions are incompatible. |
| else if (!existingBinding.getValue().equals(varValue)) { |
| return null; |
| } |
| } |
| } |
| return bindingSet; |
| } |
| } |